Means for preventing fluctuations in rotary motors.



PATENTED APR, '7,- 1903.

J. J. WOOD.

MEANS FOR PREVENTING FLUCTUATIONS IN ROTARY MOTORS.

APPLIOATION FILED MAY 31, 1900.

NO MODEL.

I VJ

Z INVENTOR:

By Azzomeys, Wi

FIG.

I WITNESSES:

UNITED STATES PATENT OFFICE.

JAMES J. WOOD, OF FORTWAYNE, INDIANA, ASSIGNOR TO THE GENERAL ELECTRICCOMPANY, A CORPORATION on NEW YORK.

MEANS FOR PREVENTING FLUCTUA TIONS IN ROTARY MOTORS.

SPECIFICATION forming part r Letters Patent No. 72 dated April 1903-Application filed May 31, 1900. Serial Ne. 18,646. (No model.)

To all whom it 177,07 concern:

Be it known that I, JAMES JJVOOD, a citizen of the United States,residing at Fort Wayne,

in the county of Allen and State of Indiana,

have invented certain new and useful Improvements in Means forPreventing Fluctuationsin Rotary Motors, of which the following is aspecification.

The object of this invention is to prevent IO or reduce fluctuationsoccurring in rotary motor devices, by which term I mean to include primemoverssuch as steam-engines,

turbines, impact wheels, or the like-and also secondary motordevicessuch, for example, as dynamo-electric generators, electricmotors, rotary converters, and thelike.

Myinvention findsits most important application to synchronousalternating dynamoelectric machines, by which term I mean to includealternating generators, alternating synchronous motors, and rotaryconverters. My invention is applicable wherever'in such a rotary motorfluctuations are liable to occur from a uniform rotation by reasoneither of variations in the propulsive energy or variations in the workor load, which variations recur at frequent intervals, so that they tendto produce alternate accelerations and retardations of the motor, suchas are known in the art as hunting or pumping.

To make my invention fully apparent, I will proceed to describe the samein its application to a synchronous alternating motor. In operating suchmotors it is well known that when the dynamo or generator fluctuates inspeed in different parts of a revolution (as occurs when the generatoris driven by an engine the propulsive thrust of which varies atdifferent periods of each revolution) 0 the motor tends to hunt orpumpthat is, its armature runs sometimes a little faster and sometimes alittle slower than the generator, with the result of causing a beatingsound in the motor and of disturbing the circuit, as

5 will beindicated hereinafter. Such hunting or beatin g action isusually indicative of some irregularity in the circuit feeding themotor. This irregularity may consist of variations either in speed or inelectromotive force.

'i'iw variation in speed of the generator tends to cause a correspondingvariation in the speed of a synchronous motor. The motor cannot,however, assume instantly the speed required by the new speed of thegenerator. When the speed of the generator increases, the motor-armaturebegins to increase in' speed; but by reason of its lagging the motorreceives an increased current, because its armature is notin normalposition for the new frequency and because additional cur- 6o rent isrequired for supplying the energy necessary for increasing its speed.This additional current produces a difference of magnetism of the field,which must again be altered when the generator speed decreases below theaverage. The motor is therefore undergoing a slight variation in speed,which seeks to approximate to, but does not ex actly correspond with,that of the generator. This pumping or rocking or hunting effect,however, will almost entirely disappear when even a small load .is puton the motor. It has heretofore been the custom to weaken the field of asynchronous motor when it was fonndto pump. The efiect of this is tolower the electromotive force of the motor,

thereby putting an artificial load on the armature, which, however,while it reduces the pumping, has the disadvantage of reducing theelectromotive force of the generator and of upsetting the line. Toovercome this defect and avoid interference with the line,

it has been proposed to applya fiy-wheel to the shaft of the motorthrough the medium of a yielding connection comprising a spring orsprings under tensile strain. It'has been found in practice, however,that this construction is not an efficient one, as the springs andconnections quickly break in use.

By my invention I aim to providean im- 0 proved construction of such adevice, wherein this defect is avoided. I Hence provide a springconnection between the fly-wheel and shaft, wherein the spring orsprings act by compression to produce the desired elfect, 5 and Iprovide stops for limiting the relative movement of the fly-wheel andmotor-shaft,

so that the degree of compression which may be applied to the springs islimited,- and provide means for guiding the springs concen- I00 tricallywith the axis of the wheel. The effeet of such fly-wheel is toprevent-the objec- 'out any pumping.

tionable pumping action referred to. If the generator speed suddenlyincreases, the armature tends to correspondingly accelerate its speed;but the fly-wheel lags behind, thereby putting a slight load on themotor, and then when the generator slows down the motor-armature tendsto run slower, while the fly-wheel, tending to run at a uniform speed,catches up with the motor-shaft and forces it ahead or resists itstendency to slow down, thereby again putting a slight load on the motor.ting a slight load on a synchronous motor extinguishes the pumpingeffect, this being equally true whether it is electrical, by weakeningthe field and taking extra current, or is mechanical, by throwing someadditional work upon the motor. Such yieldingly-connected fly-wheel isof the latter order and has the effect of causing the motor to run with-Inasmuch as the load imposed by the fly-wheel is felt only at theinslants when the variation in speed occurs, its efiect in correctingthe pumping is accompanied by less loss of energy than with a load whichimposes a continuous drag on the motor.

In the accompanying drawings, Figure l is sectional elevation of a motoror other synchronous dynamo-electric machine provided with the preferredform of my invention. Fig. 2 is a face view of the fly-wheel, showingone-half of the shaft-collar in section on the line 2 2 in Fig. 3. Fig.3 is a transverse section of the fly-wheel and collar in two planes, asdenoted by the line 3 3 in Fig. 2.

In Fig. 1 I have shown what may, for example, be understood as analternating motor of well-known type or as a rotary converter. In thisfigure,fis the field-magnet, A is the armature, b is the armatureshaft,

' c c are the collector-rings, and d d are the brushes leading thealternating current into these rings. I have shown this machine asconstructed with a commutator e for feeding I mounted a fly-wheel F. Thepreferred construction is that shown in Figs. 1 to 3, where thefiy-wheel F is loosely mounted upon a sleeve B, which itself is keyed orotherwise fixed upon the shaft. Attached to the shaft is a collar orflange C, which is preferably made in one piece with the sleeve B andwhich has one or more (preferably two) projections h h, each of whichconstitutes two opposed abutments. The fly-wheel F has preferably twoarc-shaped chambers or grooves i i,which are formed in such manner as toleave webs or abutments 2"11. The chambers it are adapted toreceive theprojections h 71. of the collar C and to inclose springs S, preferablycoiled or helical springs, as best shown in I have already stated thatput:-

Fig. 2. I preferably use four springs S, each extending between one ofthe projections h.

of the collar 0 and the adjacent abutment z" of the fly-wheel F. Eachpair of springs thus affords an elastic and resilient connection forresisting relative movement of the fiy-wheel and shaft in eitherdirection. To guide the springs in the chambers z', I preferably employaring 11., which is shown as formed in two parts and as held within thechambers i by suitable bolts 0. The webs i are preferably recessed toreceive the ring 'n, as shown in Fig. 3, which is thus held centrallywithinthe chambers i '6. Each of the springs S encircles the ring 1?,with a loose fit, so that while held in its appropriatechambeni, out ofcontact with the walls of the latter, it may move freely along the ringwhen compressed or extended by relative displacement of the flywheel andshaft. This relative movementis limited by shoulders m m, formed uponthe fly-wheel, which extend into the path of the projections h h. Therelative displacement thus provided forshould be such that ifthe fly-This and other similar modifications are,how-

ever, within the scope of my invention, which is not limited to theexact construction shown.

With the construction described the load imposed during periods of speedvariation is (in addition to unavoidable friction) proportional to thecompression of the springs, and this compression during the period oflagging is given back by the expansion of the springs during asucceeding period of acceleration, so that the load necessary tosuppress pumping is economized.

Instead 'of applying the fly-wheel directly on the armature-shaft it maybe applied on any shaft driven therefrom.

It is to be understood that my improved device may be interposed at anypoint between the fly-wheel and motor, so long as it serves to producethe effect described.

Although for convenience of illustration I have hereinhefore describedmy invention in detail as appliedto an alternating motor, it

is to be understood that my invention is by no means limited to thisspecific application.

In fact, it finds its greatest utility in its application to rotaryconverters of any of the ordinary types well known in the art, to whichit is applied in precisely the manner hereinbefore described withparticular reference to a synchronous motor. going description may beunderstood as To this end the forethough such rotary converter werespecifically mentioned in lieu of the synchronous alternating motor, andFig. 1 may be understood as specifically illustrating one type of suchrotary converter.

By the term fly-wheel as used in this specification I include not merelysuch a wheel as a mechanic would ordinarily understand by this term, butalso any suitably symmetrical mass or masses so mounted and adapted asto act in a manner substantially equivalent to the action of afly-wheel-that is to say, by rotating with the motor and by reason ofits inertia resisting any acceleration or retardation of its normalspeed of rotation.

I claim as my invention the following-defined novel features,substantially as hereinbefore specified, namely: I

1. The combination with a rotary motor, of a fly-wheel driven thereby,free to turn relatively thereto, a spring interposed betweensaidfly-wheel and motor for producing the effect described, and a guidefor said spring comprising a ring concentric with the axis of rotationof said fly-wheel.

2. The combination with a rotary motor, of a shaft rotating therewith, afly-wheel driven by said shaft and free to turn relatively thereto, saidfly-wheel having arc-shaped chambers, a collar fixed to said shafthaving proj ections entering said chambers,coi1ed springs interposedbetween said wheel and inclosed in said chambers, and guides Within saidchambers for guiding said springs therein,comprising arin g fixed tosaid fly-wheel and concentric with the axis of rotation of the latter.

3. The combination with a rotary motor, of a shaft rotating therewith, afly-wheel driven by said shaft and free to turn relatively thereto,saidfly-wheel having two arc-shaped chambers, and shoulders between saidchambers, a guide-ring extending within said chambers and fixed to saidshoulders, a collar fixed to said shaft, and having projections enteringwithin said chambers said projections embracing said ring, and foursprings each encircling said ring, and at one end bearing against one ofsaid shoulders, and at the other end bearing against one of saidprojections, whereby to resist relative movement in either direction ofsaid fiy-wheel and collar.

In witness whereof I have hereunto signed my name in the presence of twosubscribing witnesses.

A. L. HADLEY, W. H. CRIGHTON.

projections and fly-

